Although the tree traversal meant to be used here is not inherently a BST property, its output is, which is the key to the solution.

what is incorrect? can you elaborate?

Incorrect.

this is not a BST problem. it is a general BT problem. why put a misleading title?

C++ translation

Please, review and (hopefully) approve.

AWSOME ONE, MUCH BETTER THAN THE LEECODE VERSION! THE AUTHOR IS ABSOLUTE A GENIUS!

Done ;-)

Fortran 2008 should be enabled...

It seems to me that random tests occasionally include duplicate numbers what is explicitly mentioned in the task description as not happening... :-(

I feel like the most common definition of a BST has all of the left nodes <= the root node and all right nodes > the root node (ascending order). Allowing descending order BSTs is a nice twist but I think it should be mentioned in the instructions.

Thanks a lot! ;)